An electrolyte and a battery containing the same

Abstract

The application provides an electrolyte and a battery containing the electrolyte. The electrolyte satisfies 10<=B / C<=50; wherein B is the mass percentage content of the carboxylic acid ester solvent in the electrolyte, and C is the mass percentage content of the compound shown in formula 1 in the electrolyte. By simultaneously adding the carboxylic acid ester solvent and the compound shown in formula 1 in the electrolyte and optimizing the addition amount of the two, the performance of the battery can be significantly improved. By adjusting the specific surface area of the negative active material, the content of the carboxylic acid ester solvent and the compound shown in formula 1, the low-temperature discharge performance, the high-temperature storage performance and the safety performance of the battery are improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to an electrolyte and a battery containing the electrolyte. Background Technology

[0002] Lithium-ion batteries, as a new type of portable energy storage device, have been widely used in portable electronic devices such as mobile phones, laptops, and cameras due to their high energy density, high operating voltage, long cycle life, no memory effect, and green environmental protection. Their application scope is also expanding from small portable electronic devices to large electric transportation vehicles and renewable energy storage.

[0003] Electrolytes, as a key component of lithium-ion batteries, play a crucial role in transporting active lithium ions between the positive and negative electrodes, significantly impacting the battery's cycle life, capacity, interfacial performance, and safety. Commercially available electrolytes typically include lithium salts, organic solvents, and additives. The key to further improving battery performance lies in the development of additives. Commonly used electrolyte additives include film-forming, flame-retardant, water-removing and acid-reducing, overcharge protection, and conductive additives. However, at high temperatures, the performance of lithium-ion batteries deteriorates significantly, particularly in high-temperature storage and high-rate discharge. Further research is needed to develop additives that improve the high-temperature storage and low-temperature discharge performance of lithium-ion batteries. Summary of the Invention

[0004] Studies have found that lithium-ion batteries still suffer from poor high-temperature stability and difficulty in discharging in cold regions during use. The main reason for these problems is that under high voltage and / or high temperature operating conditions, the structure of the positive electrode material is damaged, leading to the dissolution of metal ions, which in turn damages the negative electrode interface film, increasing the battery's internal resistance, causing severe polarization, and thus degrading the battery's high and low temperature performance. In severe cases, it can also lead to safety problems such as thermal runaway caused by side reactions and lithium plating piercing the separator.

[0005] This invention improves the high-temperature storage, low-temperature discharge, and safety performance of batteries by introducing the compound shown in Formula 1 as an additive into the electrolyte and further optimizing the content of carboxylic acid ester solvent and the compound shown in Formula 1. On this basis, the high-temperature storage performance, low-temperature discharge performance, and safety performance of batteries are further enhanced by controlling the specific surface area of ​​the negative electrode active material and the amount of compound shown in Formula 1 added.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] An electrolyte comprising an organic solvent, a lithium electrolyte salt, and additives; the organic solvent comprising a carboxylic acid ester solvent, and the additives comprising at least one compound of Formula I:

[0008] [(1 / n)L n+ ]O - -MQR + [T - ] Formula I

[0009] In formula I, L n+ Selected from Li + K + Na + Cs + Mg 2+ Or Al 3+ ;

[0010] M is selected from -S(=O)2- or -S(=O)2-O-;

[0011] Q is selected from substituted or unsubstituted alkylene groups, substituted or unsubstituted alkoxy groups, and substituted or unsubstituted alkenyl groups; if substituted, the substituent is a cyano or halogen.

[0012] R + Selected from

[0013] Among them, R 11 R 12 R 13 R 14 and R 15 The same or different groups are independently selected from hydrogen, halogen, cyano, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted heterocyclic, and substituted or unsubstituted heteroaryl; if substituted, the substituent is halogen; R 11 R 12 R 13 R 14 and R 15 Any two groups in the structure can bond together to form a ring structure; * represents a connection point.

[0014] R 16 Selected from substituted or unsubstituted alkylene groups; if substituted, the substituent is a cyano or halogen;

[0015] R 17 R 18 They may be the same or different, and are independently selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkoxy, substituted or unsubstituted -COO-alkyl; if substituted, the substituent is cyano or halogen;

[0016] The T - Selected from PF6 - F - NO3 - PO2F2- BF4 - (FSO2)2N - ,

[0017]

[0018] At least one of them;

[0019] The electrolyte satisfies the following:

[0020] 10≤B / C≤50

[0021] Wherein, B is the mass percentage of the carboxylic acid ester solvent in the electrolyte, and C is the mass percentage of the compound shown in Formula 1 in the electrolyte.

[0022] Studies have found that when the mass percentage of the carboxylic acid ester solvent in the electrolyte and the mass percentage of the compound shown in Formula 1, B / C, satisfy 10 ≤ B / C ≤ 50, the high-temperature storage, low-temperature discharge, and safety performance of the battery can be improved.

[0023] According to an embodiment of the present invention, B / C is 10, 15, 20, 25, 30, 35, 40, 45 or 50.

[0024] According to an embodiment of the present invention, Q is selected from substituted or unsubstituted C. 1-12 Alkylene, substituted or unsubstituted C 1-12 alkeneoxy, substituted or unsubstituted C 2-12 Alkenyl group; if substituted, the substituent is cyano or halogen.

[0025] According to an embodiment of the present invention, Q is selected from substituted or unsubstituted C. 1-6 Alkylene, substituted or unsubstituted C 1-6 alkeneoxy, substituted or unsubstituted C 2-6 Alkenyl group; if substituted, the substituent is cyano or halogen.

[0026] According to an embodiment of the present invention, Q is selected from substituted or unsubstituted C. 1-3 Alkylene, substituted or unsubstituted C 1-3 alkeneoxy, substituted or unsubstituted C 2-3 Alkenyl group; if substituted, the substituent is cyano or halogen.

[0027] According to an embodiment of the present invention, R 11 R 12 R 13 R 14 and R 15 They may be the same or different, and are independently selected from hydrogen, halogen, cyano, substituted or unsubstituted C.1-12 Alkyl, substituted or unsubstituted C 2-12 alkenyl, substituted or unsubstituted C 2-12 Alkyne group, substituted or unsubstituted 3-20 membered heterocyclic group, substituted or unsubstituted 5-20 membered heteroaryl group; if substituted, the substituent is halogen; R 11 R 12 R 13 R 14 and R 15 Any two adjacent groups in the structure can bond together to form a ring structure; * represents a connection point.

[0028] According to an embodiment of the present invention, R 11 R 12 R 13 R 14 and R 15 They may be the same or different, and are independently selected from hydrogen, halogen, cyano, substituted or unsubstituted C. 1-6 Alkyl, substituted or unsubstituted C 2-6 alkenyl, substituted or unsubstituted C 2-6 Alkyne group, substituted or unsubstituted 3-12 membered heterocyclic group, substituted or unsubstituted 5-12 membered heteroaryl group; if substituted, the substituent is halogen; R 11 R 12 R 13 R 14 and R 15 Any two adjacent groups in the structure can bond together to form a ring structure; * represents a connection point.

[0029] According to an embodiment of the present invention, R 11 R 12 R 13 R 14 and R 15 They may be the same or different, and are independently selected from hydrogen, halogen, cyano, substituted or unsubstituted C. 1-3 Alkyl, substituted or unsubstituted C 2-3 alkenyl, substituted or unsubstituted C 2-3 Alkyne group, substituted or unsubstituted 3-6 membered heterocyclic group, substituted or unsubstituted 5-6 membered heteroaryl group; if substituted, the substituent is halogen; R 11 R 12 R 13 R 14 and R 15 Any two adjacent groups in the structure can bond together to form a ring structure; * represents a connection point.

[0030] According to an embodiment of the present invention, R 16 Selected from substituted or unsubstituted C 1-3Alkylene; if substituted, the substituent is a cyano or halogen.

[0031] According to an embodiment of the present invention, R 16 Selected from substituted or unsubstituted C 1-2 Alkylene; if substituted, the substituent is a cyano or halogen.

[0032] According to an embodiment of the present invention, R 17 R 18 They are the same or different, and are selected independently of substituted or unsubstituted C. 1-12 Alkyl, substituted or unsubstituted C 2-12 alkenyl, substituted or unsubstituted C 1-12 Alkyl, substituted or unsubstituted -COO-C 1-12 Alkyl group; if substituted, the substituent is cyano or halogen.

[0033] According to an embodiment of the present invention, R 17 R 18 They are the same or different, and are selected independently of substituted or unsubstituted C. 1-6 Alkyl, substituted or unsubstituted C 2-6 alkenyl, substituted or unsubstituted C 1-6 Alkyl, substituted or unsubstituted -COO-C 1-6 Alkyl group; if substituted, the substituent is cyano or halogen.

[0034] According to an embodiment of the present invention, R 17 R 18 They are the same or different, and are selected independently of substituted or unsubstituted C. 1-3 Alkyl, substituted or unsubstituted C 2-3 alkenyl, substituted or unsubstituted C 1-3 Alkyl, substituted or unsubstituted -COO-C 1-3 Alkyl group; if substituted, the substituent is cyano or halogen.

[0035] According to an embodiment of the present invention, the compound represented by Formula 1 is selected from at least one of the compounds represented by Formulas 1-1 to 1-22:

[0036]

[0037]

[0038]

[0039] According to an embodiment of the present invention, the amount of the compound shown in Formula 1 added is 0.5 wt% to 2.5 wt% of the total mass of the electrolyte, for example, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, 2 wt%, 2.1 wt%, 2.2 wt%, 2.3 wt%, 2.4 wt%, or 2.5 wt%.

[0040] According to embodiments of the present invention, the compound represented by Formula 1 can be prepared by methods known in the art or obtained through commercial purchase.

[0041] According to embodiments of the present invention, the carboxylic acid ester solvent is selected from at least one of ethyl acetate (EA), ethyl propionate (EP), or propyl propionate (PP).

[0042] According to an embodiment of the present invention, the amount of the added carboxylic acid ester solvent is 10wt% to 50wt% of the total mass of the electrolyte, for example, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, or 50wt%.

[0043] According to an embodiment of the present invention, the electrolyte lithium salt is selected from at least one of lithium hexafluorophosphate, lithium difluorophosphate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium difluorooxalate phosphate, lithium tetrafluoroborate, lithium tetrafluorooxalate phosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

[0044] According to an embodiment of the present invention, the amount of the added electrolyte lithium salt is 13wt% to 20wt% of the total mass of the electrolyte, for example, 13wt%, 14wt%, 15wt%, 16wt%, 17wt%, 18wt%, 19wt%, or 20wt%.

[0045] According to embodiments of the present invention, the organic solvent further includes carbonate solvents.

[0046] According to an embodiment of the present invention, the carbonate solvent is selected from at least two of propylene carbonate, ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, and diethyl carbonate.

[0047] The present invention also provides a battery comprising the electrolyte described above.

[0048] According to an embodiment of the present invention, the battery is a lithium-ion battery.

[0049] According to an embodiment of the present invention, the battery further includes a positive electrode, a negative electrode, and a separator.

[0050] According to an embodiment of the present invention, the positive electrode sheet includes a positive current collector and a positive active material layer coated on one or both surfaces of the positive current collector, wherein the positive active material layer includes a positive active material, a conductive agent, and a binder.

[0051] According to an embodiment of the present invention, the positive electrode active material is selected from lithium cobalt oxide or lithium cobalt oxide doped with two or more elements selected from Al, Mg, Mn, Cr, Ti, and Zr, wherein the lithium cobalt oxide doped with two or more elements selected from Al, Mg, Mn, Cr, Ti, and Zr has the chemical formula Li. x Co 1-y1-y2-y3-y4 A y1 B y2 C y3 D y4 O2; 0.95≤x≤1.05, 0.01≤y1≤0.1, 0.01≤y2≤0.1, 0≤y3≤0.1, 0≤y4≤0.1, A, B, C, and D are selected from two or more elements among Al, Mg, Mn, Cr, Ti, and Zr.

[0052] According to an embodiment of the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material, a conductive agent, and a binder.

[0053] According to an embodiment of the present invention, the negative electrode active material is selected from at least one of artificial graphite, natural graphite, hard carbon, soft carbon, mesophase carbon microspheres, silicon-based negative electrode materials and lithium-containing metal composite oxide materials.

[0054] According to an embodiment of the present invention, the mass percentage of each component in the positive electrode active material layer is: 80-99.8 wt% positive electrode active material, 0.1-10 wt% conductive agent, and 0.1-10 wt% binder.

[0055] Preferably, the mass percentage of each component in the positive electrode active material layer is: 90-99.6 wt% positive electrode active material, 0.2-5 wt% conductive agent, and 0.2-5 wt% binder.

[0056] According to an embodiment of the present invention, the mass percentage of each component in the negative electrode active material layer is: 80-99.8 wt% negative electrode active material, 0.1-10 wt% conductive agent, and 0.1-10 wt% binder.

[0057] Preferably, the mass percentage of each component in the negative electrode active material layer is: 90-99.6 wt% negative electrode active material, 0.2-5 wt% conductive agent, and 0.2-5 wt% binder.

[0058] According to an embodiment of the present invention, the conductive agent is selected from at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, and metal powder.

[0059] According to an embodiment of the present invention, the adhesive is selected from at least one of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.

[0060] According to an embodiment of the present invention, the battery satisfies:

[0061] 0.6≤A / C≤5

[0062] Where A is the specific surface area of ​​the negative electrode active material, in m². 2 / g, where C is the mass percentage of the compound represented by Formula 1 in the electrolyte.

[0063] Studies have found that when the ratio of the specific surface area of ​​the negative electrode active material in the electrolyte to the mass percentage content of the compound shown in Formula 1, A / C, satisfies 0.6≤A / C≤5, the high-temperature storage performance, low-temperature discharge performance, and safety performance of the battery are further improved.

[0064] According to an embodiment of the present invention, the value range of A is 0.5m. 2 / g~5m 2 / g, for example, 0.5m 2 / g、1m 2 / g、2m 2 / g、3m 2 / g、4m 2 / g or 5m 2 / g.

[0065] According to an embodiment of the present invention, the charging cut-off voltage of the battery is 4.45V or higher.

[0066] Terminology and Explanation:

[0067] The term "halogen" refers to F, Cl, Br, and I. In other words, F, Cl, Br, and I can be described as "halogens" in this specification.

[0068] Term "C" 1-12 "alkyl" should be understood to preferably represent a straight-chain or branched saturated monovalent hydrocarbon group having 1 to 12 carbon atoms, preferably C12. 1-10 Alkyl group. "C" 1-10"alkyl" should be understood to preferably represent a straight-chain or branched saturated monovalent hydrocarbon group having 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms. The alkyl group is, for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, 2-methylbutyl, 1-methylbutyl, 1-ethylpropyl, 1,2-dimethylpropyl, neopentyl, 1,1-dimethylpropyl, 4-methylpentyl, 3-methylpentyl, 2-methylpentyl, 1-methylpentyl, 2-ethylbutyl, 1-ethylbutyl, 3,3-dimethylbutyl, 2,2-dimethylbutyl, 1,1-dimethylbutyl, 2,3-dimethylbutyl, 1,3-dimethylbutyl, or 1,2-dimethylbutyl, etc., or isomers thereof. In particular, the group has 1, 2, 3, 4, 5, or 6 carbon atoms ("C"). 1-6 Alkyl groups, such as methyl, ethyl, propyl, butyl, isopropyl, isobutyl, sec-butyl, tert-butyl, and more particularly, the groups having 1, 2, or 3 carbon atoms (“C”). 1-3 Alkyl), such as methyl, ethyl, n-propyl or isopropyl.

[0069] Term "C" 2-12 "Alkenyl" should be understood to preferably represent a straight-chain or branched monovalent hydrocarbon group containing one or more double bonds and having 2 to 12 carbon atoms, preferably "C". 2-10 "Alkenyl". "C" 2-10 "Alkenyl" should be understood to preferably represent a straight-chain or branched monovalent hydrocarbon group containing one or more double bonds and having 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms, particularly 2 or 3 carbon atoms ("C"). 2-3The term "alkenyl" should be understood to refer to a group containing more than one double bond, where the double bonds can be separable or conjugated. The alkenyl group is, for example, vinyl, allyl, (E)-2-methylvinyl, (Z)-2-methylvinyl, (E)-but-2-enyl, (Z)-but-2-enyl, (E)-but-1-enyl, (Z)-but-1-enyl, pent-4-enyl, (E)-pent-3-enyl, (Z)-pent-3-enyl. -alkenyl, (E)-pent-2-enyl, (Z)-pent-2-enyl, (E)-pent-1-enyl, (Z)-pent-1-enyl, hex-5-enyl, (E)-hex-4-enyl, (Z)-hex-4-enyl, (E)-hex-3-enyl, (Z)-hex-3-enyl, (E)-hex-2-enyl, (Z)-hex-2-enyl, (E)-hex-1-enyl, (Z)-hex-1-enyl, isopropenyl, 2 -Methylprop-2-enyl, 1-methylprop-2-enyl, 2-methylprop-1-enyl, (E)-1-methylprop-1-enyl, (Z)-1-methylprop-1-enyl, 3-methylbut-3-enyl, 2-methylbut-3-enyl, 1-methylbut-3-enyl, 3-methylbut-2-enyl, (E)-2-methylbut-2-enyl, (Z)-2-methylbut-2-enyl, (E)-1-methylbut-2-enyl 1,1-dimethylprop-2-enyl, (Z)-1-methylbut-2-enyl, (E)-3-methylbut-1-enyl, (Z)-3-methylbut-1-enyl, (E)-2-methylbut-1-enyl, (Z)-2-methylbut-1-enyl, (E)-1-methylbut-1-enyl, (Z)-1-methylbut-1-enyl, 1,1-dimethylprop-2-enyl, 1-ethylprop-1-enyl, 1-propylvinyl, 1-isopropylvinyl.

[0070] Term "C" 2-12 "Alkyne group" should be understood as representing a straight-chain or branched monovalent hydrocarbon group containing one or more triple bonds and having 2 to 12 carbon atoms, preferably "C2-C". 10 "Alkyne group". The term "C2-C" 10"Alynyl" should be understood to preferably represent a straight-chain or branched monovalent hydrocarbon group containing one or more triple bonds and having 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms, particularly 2 or 3 carbon atoms ("C2-C3-alkynyl"). The alkynyl group is, for example, ethynyl, propynyl, propynyl-2-alkynyl, butynyl, butynyl-2-alkynyl, butynyl-3-alkynyl, pentynyl, pentynyl-2-alkynyl, pentynyl-3-alkynyl, pentynyl-4-alkynyl, hexynyl, hexynyl-2-alkynyl, hexynyl-3-alkynyl, hexynyl-4-alkynyl, hexynyl-5-alkynyl, 1-methylpropynyl-2-alkynyl, 2-methylbutynyl-3-alkynyl, 1-methylbutynyl-3-alkynyl, 1-methylbutynyl-2-alkynyl, 3-methylbutynyl-1-alkynyl, 1 -Ethylprop-2-ynyl, 3-methylpentan-4-ynyl, 2-methylpentan-4-ynyl, 1-methylpentan-4-ynyl, 2-methylpentan-3-ynyl, 1-methylpentan-3-ynyl, 4-methylpentan-2-ynyl, 1-methylpentan-2-ynyl, 4-methylpentan-1-ynyl, 3-methylpentan-1-ynyl, 2-ethylbutan-3-ynyl, 1-ethylbutan-3-ynyl, 1-ethylbutan-2-ynyl, 1-propylpropan-2-ynyl, 1-isopropylpropan-2-ynyl, 2,2-dimethylbutan-3-ynyl, 1,1-dimethylbutan-3-ynyl, 1,1-dimethylbutan-2-ynyl, or 3,3-dimethylbutan-1-ynyl. In particular, the ynyl group is ethynyl, propan-1-ynyl, or propan-2-ynyl.

[0071] The term "3-20 membered heterocyclic group" refers to a saturated or unsaturated monovalent monocyclic or bicyclic hydrocarbon ring containing 1-5 heteroatoms independently selected from N, O, and S, preferably a "3-10 membered heterocyclic group". The term "3-10 membered heterocyclic group" also refers to a saturated monovalent monocyclic or bicyclic hydrocarbon ring containing 1-5, preferably 1-3, heteroatoms selected from N, O, and S. The heterocyclic group can be connected to the rest of the molecule via any one of the carbon atoms or a nitrogen atom (if present). Specifically, the heterocyclic group can include, but is not limited to: 4-membered rings, such as azirmonobutyl or oxobutyl; 5-membered rings, such as tetrahydrofuranyl, dioxacyclopentenyl, pyrrolyl, imidazoyl, pyrazolyl, or pyrrololinyl; or 6-membered rings, such as tetrahydropyranyl, piperidinyl, morpholinyl, dithiaalkyl, thiomorpholinyl, piperazinyl, or trithiaalkyl; or 7-membered rings, such as diazacycloheptyl. Optionally, the heterocyclic group may be benzo-fused. The heterocyclic group may be bicyclic, for example, but not limited to, a 5,5-membered ring, such as a hexahydrocyclopentano[c]pyrrole-2(1H)-yl ring, or a 5,6-membered bicyclic ring, such as a hexahydropyrrolo[1,2-a]pyrazin-2(1H)-yl ring. The nitrogen-containing ring may be partially unsaturated, i.e., it may contain one or more double bonds, for example, but not limited to, 2,5-dihydro-1H-pyrrole, 4H-[1,3,4]thiadiazinyl, 4,5-dihydrooxazolyl, or 4H-[1,4]thiazinyl, or it may be benzo-fused, for example, but not limited to, dihydroisoquinolinyl. According to the invention, the heterocyclic group is non-aromatic.

[0072] The term "5-20-membered heteroaryl" should be understood to include monovalent monocyclic, bicyclic, or tricyclic aromatic ring systems having 5 to 20 ring atoms and containing 1 to 5 heteroatoms independently selected from N, O, and S, such as "5-14-membered heteroaryl". The term "5-14-membered heteroaryl" should also be understood to include monovalent monocyclic, bicyclic, or tricyclic aromatic ring systems having 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14 ring atoms, particularly 5, 6, 9, or 10 carbon atoms, and containing 1 to 5, preferably 1 to 3, heteroatoms independently selected from N, O, and S, and in each case, may be benzofused. Specifically, the heteroaryl group is selected from thienyl, furanyl, pyrroleyl, oxazolyl, thiazolyl, imidazoleyl, pyrazolyl, isoxazolyl, isothiazolyl, oxadiazolyl, triazolyl, thiadiazolyl, thia-4H-pyrazolyl, and their benzo[derivatives], such as benzofuranyl, benzothienyl, benzooxazolyl, benzoisooxazolyl, benzoimidazolyl, benzotriazolyl, indazole, indolyl, isindolyl, etc.; or pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, and their benzo[derivatives], such as quinolinyl, quinazolinyl, isoquinolinyl, etc.; or acrylinyl, inazinyl, purinyl, and their benzo[derivatives]; or terpenolyl, phthalazinyl, quinazolinyl, quinoxolinyl, naphridinyl, pteridinyl, carbazolyl, acridineyl, phenazinyl, phenothiazinyl, phenothiazinyl, etc.

[0073] The beneficial effects of this invention are:

[0074] This invention provides an electrolyte and a battery containing the electrolyte. Battery performance can be significantly improved by simultaneously adding a carboxylic acid ester solvent and the compound shown in Formula 1 to the electrolyte and optimizing the amounts of both. Specifically, using a carboxylic acid ester solvent reduces the viscosity of the electrolyte, improving the battery's kinetic performance. The compound shown in Formula 1 has a higher HOMO energy level than the solvent molecules, allowing it to preferentially oxidize and decompose at the positive electrode surface to form a CEI film. Furthermore, its LUMO energy level is lower than the solvent molecules, allowing it to preferentially reduce at the negative electrode interface to form a SEI film. The addition of the compound shown in Formula 1 improves the stability of the interface between the positive and negative electrodes and the electrolyte, reduces side reactions between the positive and negative electrodes and the electrolyte, reduces or even eliminates gas generation, and effectively improves the battery's low-temperature discharge performance and high-temperature storage performance. In addition, by reducing battery gas generation, safety accidents caused by gas generated from side reactions breaking through the aluminum-plastic film can be avoided, as can furnace temperature failure, effectively improving the battery's safety performance. Based on this, the specific surface area of ​​the negative electrode active material and the amount of compound shown in Formula 1 are further optimized so that the specific surface area of ​​the compound shown in Formula 1 can be better matched with that of the negative electrode active material, thus providing better protection for the negative electrode. This avoids the situation where the mass percentage of the compound shown in Formula 1 is too high, which would result in insufficient gas generation to break through the aluminum-plastic film during furnace temperature testing, leading to thermal runaway and deterioration of its safety performance. It also avoids the situation where the mass percentage of the compound shown in Formula 1 is too low, which would result in insufficient protection for the negative electrode, leading to increased side reactions at the negative electrode interface and deterioration of its high and low temperature performance.

[0075] In summary, by adjusting the specific surface area of ​​the negative electrode active material, the content of carboxylic acid ester solvents and the compound shown in Formula 1, the low-temperature discharge performance, high-temperature storage performance and safety performance of the battery can be improved. Detailed Implementation

[0076] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0077] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0078] Preparation of lithium-ion batteries

[0079] (1) Preparation of positive electrode

[0080] The positive electrode active material LiCoO2 (LCO), the binder polyvinylidene fluoride (PVDF), and the conductive agent acetylene black were mixed in a weight ratio of 96.5:2:1.5. N-methylpyrrolidone (NMP) was added, and the mixture was stirred under vacuum until a uniform and fluid positive electrode slurry was formed. The positive electrode slurry was uniformly coated onto an aluminum foil with a thickness of 12 μm. The coated aluminum foil was baked in an oven with five different temperature gradients, and then dried in an oven at 120°C for 8 hours. After rolling and die-cutting, the positive electrode sheet was obtained.

[0081] (2) Preparation of negative electrode sheet

[0082] Artificial graphite (with a specific surface area A), sodium carboxymethyl cellulose (CMC-Na) as a thickener, styrene-butadiene rubber as a binder, acetylene black as a conductive agent, and single-walled carbon nanotubes (SWCNTs) as a conductive agent were mixed in a weight ratio of 95.9:1:1.8:1:0.3. Deionized water was added, and the mixture was stirred in a vacuum mixer to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated onto a copper foil with a thickness of 8 μm. After drying (temperature: 85℃, time: 5h), rolling, and die-cutting, a negative electrode sheet was obtained.

[0083] (3) Electrolyte preparation

[0084] In an argon-filled glove box (moisture <10 ppm, oxygen <1 ppm), ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), and carboxylic acid ester solvents (specific selections shown in Table 1) were mixed thoroughly. Then, fully dried lithium salt LiPF6 was dissolved in the above solvents, and the compound shown in Formula 1 (specific structure shown in Table 1) was added to obtain the electrolyte. In the electrolyte, the mass percentages of LiPF6, EC, PC, and carboxylic acid ester solvents were 14.5%, C, and DEC, respectively.

[0085] (4) Preparation of the diaphragm

[0086] An 8μm thick coated polyethylene diaphragm was selected.

[0087] (5) Preparation of lithium-ion batteries

[0088] The prepared positive electrode sheet, separator, and negative electrode sheet are wound to obtain a bare cell without electrolyte injection; the bare cell is placed in an outer packaging foil, and the prepared electrolyte is injected into the dried bare cell. After vacuum sealing, standing, formation, secondary sealing, sorting and other processes, the desired lithium-ion battery is obtained.

[0089] The lithium-ion batteries of Comparative Examples 1-8 and Examples 1-9 were all prepared according to the above preparation method. The specific combinations and contents are shown in Table 1. " / " indicates that the corresponding preparation parameters are not present. The electrochemical performance test results of the lithium-ion batteries of Comparative Examples 1-8 and Examples 1-9 are shown in Table 2.

[0090] Table 1. Composition of the electrolyte in lithium-ion batteries of Comparative Examples 1-8 and Examples 1-9

[0091]

[0092] (1) 45℃ Cyclic Experiment: The batteries obtained in the above examples and comparative examples were placed in an environment of (45±2)℃ and left to stand for 2-3 hours. When the battery body reached (45±2)℃, the battery was charged at 1C constant current and constant voltage until 4.45V was cut off and the current was 0.05C. After the battery was fully charged, it was left to stand for 5 minutes, and then discharged at 1C constant current until the cutoff voltage was 3.0V. The highest discharge capacity of the first 3 cycles was recorded as the initial capacity Q. When the required number of cycles was reached, the discharge capacity Q1 of the last cycle of the battery was recorded. The results are shown in Table 2.

[0093] The calculation formula used is as follows: Capacity retention rate (%) = Q1 / Q × 100%.

[0094] (2) -10℃ low temperature discharge experiment: At 25℃, the lithium-ion battery was discharged at a constant current of 0.5C to the cutoff voltage of 3V. After resting for 10min, it was charged at a constant current and constant voltage of 1C to 4.45V with a cutoff current of 0.05C. The cell was then moved to a -10℃ high and low temperature chamber and rested for 120min. After resting, it was discharged at a constant current of 4C to the cutoff voltage of 3.0V. The inflection point voltage was recorded, and the results are shown in Table 2.

[0095] (3) Thickness expansion change after 30D storage at 60℃: The batteries prepared in the above examples and comparative examples were charged at 1C constant current and constant voltage to 4.45V with a cutoff current of 0.05C and the thickness of the fully charged battery was measured. Then, they were stored in a constant temperature chamber at 60±2℃ for 30D and the thickness of the fully charged battery was measured again. The results are shown in Table 2.

[0096] (4) Charge the battery at 1C constant current and constant voltage until it reaches 4.45V and the cutoff current is 0.05C. Place the fully charged battery in an explosion-proof oven and heat it to 132℃ at a heating rate of 5℃ / min. Keep it at this temperature for one hour and observe the gas production of the battery and whether the battery catches fire during this process.

[0097] Table 2. Electrochemical performance test results of lithium-ion batteries in Comparative Examples 1-8 and Examples 1-9

[0098]

[0099]

[0100] The electrolyte in Comparative Example 1 lacks carboxylic acid ester solvents and the compound shown in Formula 1, resulting in complete failure at low temperatures and furnace temperatures due to the negative electrode reducing electrolyte. The electrolyte in Comparative Example 2, also lacking the compound shown in Formula 1, showed improved kinetics, but the negative electrode reducing electrolyte still caused furnace temperature failure. The electrolyte in Comparative Example 3 contained too few carboxylic acid ester solvents, leading to poor battery kinetics and low-temperature performance. The electrolyte in Comparative Example 4 contained too many carboxylic acid ester solvents, resulting in poor electrolyte thermal stability and poor high-temperature cycling. The battery in Comparative Example 5 had an excessively large specific surface area of ​​negative electrode active material. The small size of the electrolyte in Comparative Example 6 resulted in insufficient gas production from side reactions during furnace temperature testing, which was insufficient to break through the aluminum-plastic film and cause thermal runaway and fire. The excessively large specific surface area of ​​the negative electrode active material in Comparative Example 6 led to insufficient interface protection, resulting in electrolyte reduction and decomposition, which deteriorated high-temperature cycling performance and also caused thermal runaway and fire. The electrolyte in Comparative Example 7 contained too little of the compound shown in Formula 1, resulting in insufficient interface protection and poor high-temperature cycling performance. The electrolyte in Comparative Example 8 contained too much of the compound shown in Formula 1, resulting in high film-forming resistance and high polarization, which deteriorated high-temperature cycling performance and low-temperature discharge performance.

[0101] Examples 1-9 show that adjusting the specific surface area of ​​the negative electrode active material in the battery, the content of solvents such as carboxylic acids in the electrolyte, and the content of the compound shown in Formula 1 can optimize the battery performance, resulting in optimal high and low temperature performance and excellent safety performance.

[0102] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A battery, characterized in that, The battery includes an electrolyte, which comprises an organic solvent, a lithium electrolyte salt, and additives; the organic solvent includes a carboxylic acid ester solvent, and the additives include at least one compound of Formula I: [(1 / n)L n+ O - -M-Q-R + [T - Formula I In formula I, L n+ Selected from Li + ; M is selected from -S(=O)2-O-; Q is selected from substituted or unsubstituted alkylene groups; R + Selected from ; Among them, R 18 Selected from alkyl groups; The T - Selected from PF6 - F - NO3 - PO2F2 - BF4 - (FSO2)2N - , At least one of them; The electrolyte satisfies the following: 10≤B / C≤50 Wherein, B is the mass percentage of the carboxylic acid ester solvent in the electrolyte, and C is the mass percentage of the compound shown in Formula 1 in the electrolyte; The amount of the compound shown in Formula 1 added is 0.5wt% to 2.5wt% of the total mass of the electrolyte; the amount of the carboxylic acid ester solvent added is 10wt% to 50wt% of the total mass of the electrolyte. The battery satisfies: 0.6≤A / C≤5 Where A is the specific surface area of ​​the negative electrode active material, in m². 2 / g, where C is the mass percentage of the compound shown in Formula 1 in the electrolyte; The carboxylic acid ester solvent is selected from at least one of ethyl acetate (EA), ethyl propionate (EP), or propyl propionate (PP); the value of A is in the range of 0.5m. 2 / g~5m 2 / g.

2. The battery according to claim 1, characterized in that, Q is selected from substituted or unsubstituted C. 1-12 Alkylene; R 18 Selected from C 1-12 alkyl.

3. The battery according to claim 2, characterized in that, Q is selected from substituted or unsubstituted C. 1-6 Alkylene; R 18 Selected from C 1-6 alkyl.

4. The battery according to claim 3, characterized in that, The compound shown in Formula 1 is selected from the compounds shown in Formula 1-21 or Formula 1-22: Formula 1-21 Equation 1-22.

5. The battery according to claim 1, characterized in that, The organic solvent also includes carbonate solvents, which are selected from at least two of propylene carbonate, ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate, and diethyl carbonate.

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